For the last five years I have worked to analyze the control system that regulates potassium. This analysis will continue, with the functions of the different components analyzed separately under uniform conditions so that the data may be combined. A mathematical model of the control system has been developed and will be expanded for use in developing and testing hypotheses. Factors important in short-term potassium regulation will be studied experimentally including: 1) effects of the Beta-adrenergic system on K regulation, 2) interaction between the K control system and the insulin-glucose control system, 3) interactions between plasma K and angiotensin II in aldo-sterone regulation, 4) and time courses of action of factors affecting K distribution and excretion. The analysis of effects of changes in plasma K and K balance on renal and cardiovascular function will continue. The following areas will be studied: effects of sustained changes in K on 1) pumping ability of the heart, 2) neural control of the circulation, 3) control of vascular smooth muscle, 4) renal function, 5) blood pressure regulation, 6) osmotic regulation, and 7) glucose regulation. Currently, there is only a rudimentary understanding of K regulation and the effects of abnormal K concentration on the major organ systems. The results of the projects proposed herein will provide information and understanding in these areas which will improve management of a large portion of the health care problems of the nation, including heart disease, hypertension, diabetes mellitus, surgical stress and numerous conditions associated with old age.